When lymph node biopsies of lymphocytic neoplasms are studied with subtle morphological and immunohistochemical methods meaningful information is obtained, that is not only of theoretical value, but which also relates to the clinical behavior ("leukemia," paraproteinemia, prognosis). Such an analysis allows us to differentiate three subtypes of chronic lymphocytic leukemia (diffuse, pseudofollicular and tumor forming) and to recognize two subtypes of immunocytoma (lympho plasmacytoid and lympho plasmacytic). The plasmacytoid-plasmacytic differentiation is usually not recognizable in blood smears. CLL cells show only IgM + IgD on their surfaces, whereas in immunocytoma monotypic cytoplasmic immunoglobulins are evident, and they are not only of the IgM type. The CD5 negative lymphoplasmacytic subtype differs clearly from chronic lymphocytic leukemia and from the majority of cases of lymphoplasmacytoid immunocytoma, which are CD5 positive.